Mario Forever is an unofficial remake of the famous Super Mario Bros. with some improvements and additions: better graphics, music and sound effect, an intro with a detailed story, difficulty choices (though it may take time for players to discover this function), lives exchange for mushroom and flower, automatic saving function, easier re-designed levels, additional rooms, platforms and secrets. Since this game is a remake, the basic gameplay is not different from the original game. The graphic are in 2D.
info: https://www.mobygames.com/game/windows/mario-forever
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These are all the versions that were ever released in Softendo's website, from 2004 up to 2017, through version 1.6. to 7.01a. While these are all virus free, the installer comes embed with the infamous Mario Forever toolbar, keep that in mind while installing these in your PC.